Hybrid 2D/3D Graphitic Carbon Nitride-Based High-Temperature Position-Sensitive Detector

Ultraviolet position-sensitive detectors(PSDs)are expected to undergo harsh environments,such as high temperatures,for a wide variety of applications in military,civilian,and aerospace.However,no report on relevant PSDs operating at high temperatures can be found up to now.Herein,we design a new 2D/3D graphitic carbon nitride(g-C_(3)N_(4))/gallium nitride(GaN)hybrid heterojunction to construct the ultraviolet high-temperature-resistant PSD.The g-C_(3)N_(4)/GaN PSD exhibits a high position sensitivity of 355 mV mm^(-1),a rise/fall response time of 1.7/2.3 ms,and a nonlinearity of 0.5%at room temperature.The ultralow formation energy of-0.917 eV atom^(-1)has been obtained via the thermodynamic phase stability calculations,which endows g-C_(3)N_(4)with robust stability against heat.By merits of the strong built-in electric field of the 2D/3D hybrid heterojunction and robust thermo-stability of g-C_(3)N_(4),the g-C_(3)N_(4)/GaN PSD delivers an excellent position sensitivity and angle detection nonlinearity of 315 mV mm^(-1)and 1.4%,respectively,with high repeatability at a high temperature up to 700 K,outperforming most of the other counterparts and even commercial silicon-based devices.This work unveils the high-temperature PSD,and pioneers a new path to constructing g-C_(3)N_(4)-based harsh-environment-tolerant optoelectronic devices.

Fragmentation behavior of large-caliber PELE impacting RHA plate at low velocity

Impact experiments of large-caliber PELE with various inner-outer diameter ratio perforating RHA plate at low velocity were performed.Experimental results showed the size of perforated holes on plate,average diameter of damage area on witness plate,and number of behind-armor fragments will increase as d/D increasing from 0.72 to 0.84.Expansion and fragmentation of large-caliber PELE in this condition were also numerically studied with ANSYS Autodyn.Then,an analytical model accounting for an additional radial shock wave was presented to predict radial expansion velocity and fragmentation of jacket,as well as an empirical approach to estimate diameter of damage area.Calculation results by these approaches were in good agreement with experiments and numerical simulations.Further discussion revealed that Shock/rarefaction wave interactions behavior varying with inner-outer diameter ratio is an important mechanism resulting in different lateral effect by PELE projectiles with various configurations.

Effect of projectile parameters on opening behavior of PELE penetrating RC target

When a penetrator with enhanced lateral effect(PELE) impacts on a reinforced concrete(RC) target,the target is damaged with a large opening.An understanding of how PELE projectile parameters affect the opening dimension,is essential for effective design of the PELE projectile.In this study,under the condition that the impact velocity and target parameters(strength and thickness) were fixed values,the important influence factors of the PELE(jacket wall thickness B,jacket material strength Y1,filling material strength Y2 and angle of monolithic jacket θ) were determined by a dimensional analysis.Tests and simulations of the PELE penetrating the RC target were conducted to analyze the influence of these factors on opening diameter(D,an equivalent diameter under relative kinetic energy).Based on the test and simulation results,it is found that the influence of these factors B,Y1 and θ on the deformation mode of the jacket shows a similar trend:as values of the three factors decrease,the jacket deforms from small bending deformation to large one,and then to curling deformation.This causes the opening diameter to first increase with the decrease of these three factors,and then decreases.It is well known that the bending resistance of the jacket is related to these factors B,Y1 and θ.Therefore,a plastic limit bending moment(M0) of the jacket was quoted to characterize the influence of these factors on the bending deformation of the jacket and the opening diameter of the target.The influence factor Y2 causes D to first increase with the increase of Y2,and then decreases.A formula was developed to predict the opening diameter,whose influence parameters were considered in a dimensionless way.It has been shown that the dimensionless opening diameter D/d1 is dependent on two dimensionless parameters■ and■,where d1 and fc are the outer diameter of the projectile and the compressive strength of the target,respectively.

Study on fragmentation of PELE against thin targets

The fragments mass and size from penetrator with enhanced lateral effect （PELE） perforating thin rolled homogenous armor （RHA） target was characterized through theoretical and numerical methods. An analytical model based on energy-limited spall （ELS） was proposed to predict fragments mass distribution of PELE with different cores and impact velocities. For different cores the expansion can be represented by a scaling factor l in the analytical calculation. The explicit finite-element （FE）-analysis of PELE fragmentation was implemented with stochastic failure criterion in AUTODYN-3D code. By statistical distribution of ＂weak points＂ in numerical model of PELE, the dynamic fragmentation was delineated to simulate Flaw-limited spall as in real material. To verify the accuracy of theoretical calculation and validate numerical results, experiments of PELE perforating thin RHA target was setup, fragments were collected by using recovery cabin filled with foam and soft sands. Both energy limited spall theory and Flaw limited approach showed accurate results compared with experimental data.

Infrared laser-induced fast photovoltaic effect observed in orthorhombic tin oxide film

The SnO_2/SnO with an orthorhombic structure is a material known to be stable at high pressures and temperatures and expected to have new optical and electrical properties. The authors report a new finding of the infrared laser induced a fast photovoltaic effect arising from orthorhombic tin oxide film with an indirect band gap（~2.4 e V） which is deposited by pulsed laser deposition. The rising time of the photovoltaic signal is about 3 ns with a peak value of 4.48 mV under the pulsed laser beam with energy density 0.015 m J/mm^2. The relation between the photovoltages and laser positions along the line between two electrodes of the film is also exhibited. A possible mechanism is put forward to explain this phenomenon.All data and analyses demonstrate that the orthorhombic tin oxide with an indirect band gap could be used as a candidate for an infrared photodetector which can be operated at high pressures and temperatures.

Shear failure behaviors and degradation mechanical model of rockmass under true triaxial multi-level loading and unloading shear tests

The redistribution of three-dimensional(3D)geostress during underground tunnel excavation can easily induce to shear failure along rockmass structural plane,potentially resulting in engineering disasters.However,the current understanding of rockmass shear behavior is mainly based on shear tests under2D stress without lateral stress,the shear fracture under 3D stress is unclear,and the relevant 3D shear fracture theory research is deficient.Therefore,this study conducted true triaxial cyclic loading and unloading shear tests on intact and bedded limestone under different normal stress σ_(n) and lateral stressσ_(p)to investigate the shear strength,deformation,and failure characteristics.The results indicate that under differentσ_(n)and σ_(p),the stress–strain hysteresis loop area gradually increases from nearly zero in the pre-peak stage,becomes most significant in the post-peak stage,and then becomes very small in the residual stage as the number of shear test cycles increases.The shear peak strength and failure surface roughness almost linearly increase with the increase inσ_(n),while they first increase and then gradually decrease asσ_(p)increases,with the maximum increases of 12.9%for strength and 15.1%for roughness.The shear residual strength almost linearly increases withσ_(n),but shows no significant change withσ_(p).Based on the acoustic emission characteristic parameters during the test process,the shear fracture process and microscopic failure mechanism were analyzed.As the shear stressτincreases,the acoustic emission activity,main frequency,and amplitude gradually increase,showing a significant rise during the cycle near the peak strength,while remaining almost unchanged in the residual stage.The true triaxial shear fracture process presents tensile-shear mixture failure characteristics dominated by microscopic tensile failure.Based on the test results,a 3D shear strength criterion considering the lateral stress effect was proposed,and the determination methods and evolution of the shear modulus G,cohesion c_(jp),friction angleφ_(jp),and dilation angleψjpduring rockmass shear fracture process were studied.Under differentσ_(n)andσ_(p),G first rapidly decreases and then tends to stabilize;cjp,φ_(jp),andψjpfirst increase rapidly to the maximum value,then decrease slowly,and finally remain basically unchanged.A 3D shear mechanics model considering the effects of lateral stress and shear parameter degradation was further established,and a corresponding numerical calculation program was developed based on3D discrete element software.The proposed model effectively simulates the shear failure evolution process of rockmass under true triaxial shear test,and is further applied to successfully reveal the failure characteristics of surrounding rocks with structural planes under different combinations of tunnel axis and geostress direction.

Near-infrared lateral photovoltaic effect of epitaxial LaTiO--_(3+δ) films under high pressure

A lateral photovoltaic effect （LPE） is discovered in an LaTiO3＋8 film epitaxially grown on a （100） SrTiO3 substrate. Under the illumination of a continuous 808 nm laser beam that is focused on the LaTiO3＋δ film through the SrTiO3 substrate, the open-circuit photovoltage depends linearly on the illuminated position. The sensitivity of the LPE can be modified by the bias current. The LaTiO3＋δ film shows a stable photoelectric property under the high pressure, up to 9 MPa. These results indicate that the LaTiO3＋δ films can give rise to a potentially photoelectronic device for near-infrared position-sensitive detection in high-pressure environments.

Effect of Acupuncture on Monoamines and Adenosine Triphosphatase Activityin Lateral Hypothalamic Area of ObeseRats

Objective: To study the mechanism of acupuncture in treating simple obesity. Methods: Central nerve push-pull perfusion and biochemical technique were used to observe the effect of acupuncture on the obese parameters, changes of monoamine transmitters and activity of ATPase in the lateral hypothalamic area (LHA) of obese rats. Results: Noradrenaline (NA) level in LHA of obese rats was higher but serotonin (5-HT) level and ATPase activity were lower than those in normal rats. After acupuncture treatment, in the same time of reducing body weight, NA level in LHA of rats was reduced, and 5-HT level and ATPase activity in it were increased.(P<0.05 and P<0.01). Conclusion:The effective regulation on LHA of obese rats is possibly one of the key factors in anti-obesity effect of acupuncture.

Temperature and metal composition dependence of lateral photovoltaic effect in Al-Alq_3/SiO_2/Si structures

A series of Al=-（Alq3）l-x granular films is prepared on Si wafer with native oxide layer using co-evaporation technique. Large lateral photovoltaic effect （LPE） is observed, with an optimal LPV sensitivity of 75 mV/mm in x=0.35 sample. The dependence of LPE on temperature and A1 composition is investigated, and the possible mechanism is discussed.

The Effect of Lateral Guiding Mechanism on Noise Characteristics in Semiconductor Lasers

A comparison between intensity noise spectra and also the line shapes of gain-guided, weakly-index-guided, and strongly-index-guided semiconductor lasers are made using numerical solution of Maxwell-Bloch equations including spontaneous emission noise.

A laterally graded junctionless transistor

This paper proposes a laterally graded junctionless transistor taking peak doping concentration near the source and drain region, and a gradual decrease in doping concentration towards the center of the channel to improve the I OFF and I ON/I OFF ratio. The decrease of doping concentration in the lateral direction of the channel region depletes a greater number of charge carriers compared to the uniformly doped channel in the OFF-state,which in turn suppresses the OFF state current flowing through the device without greatly affecting the ON state current.

Position-sensitive detectors based on two-dimensional materials

Two-dimensional(2D)materials have attracted great attention in optoelectronics because of their unique structure,optical and electrical properties.Designing high-performance photodetectors and implementing their applications are eager to promote the development of 2D materials.Position-sensitive detector(PSD)is an optical inspection device for the precise measurements of position,distance,angle,and other relevant physical variables.It is a widely used component in the fields of tracking,aerospace,nanorobotics,and so forth.Essentially,PSD is also a photodetector based on the lateral photovoltaic effect(LPE).This article reviews recent progress in high-performance PSD based on 2D materials.The high-sensitive photodetectors and LPE involved in 2D photodetectors are firstly discussed.Then,we introduce the research progress of PSD based on 2D materials and analyze the carrier dynamics in different device structures.Finally,we summarize the functionalities and applications of PSD based on 2D materials,and highlight the challenges and opportunities in this research area.

Ultrasensitive broadband position-sensitive detector based on graphitic carbon nitride

As a typical two-dimensional material,graphitic carbon nitride(g-CN)has attracted great interest because of its distinctive electronic,optical,and catalytic properties.However,the absence of a feasible route toward large-area and high-quality films hinders its development in optoelectronics.Herein,high-quality g-CN films have been grown on Si substrate via a vapor-phase transport-assisted condensation method.The g-CN/Si heterojunction shows an obvious response to ultraviolet–visible-near infrared photons with a responsivity of 133 A·W−1,which is two orders of magnitude higher than the best value ever reported for g-CN photodetectors.A position-sensitive detector(PSD)has been developed using the lateral photovoltaic effect of the g-CN/Si heterojunction.The PSD shows a wide response spectrum ranging from 300 to 1,100 nm,and a position sensitivity and rise/decay time of 395 mV·mm−1 and 3.1/50μs,respectively.Moreover,the application of the g-CN/Si heterojunction photodetector in trajectory tracking and acoustic detection has been realized for the first time.This work unveils the potential of g-CN for large-area photodetectors,and prospects for their applications in trajectory tracking and acoustic detection.

Damage-constitutive model for seawater coral concrete using different stirrup confinements subjected to axial loading

Recently,the application of detrital coral as an alternative to natural aggregates in marine structures has attracted increased attention.In this study,research on the compressive performance of coral aggregate concrete(CAC)confined using steel stirrups with anti-rust treatment was experimentally conducted.A total of 45 specimens were cast,including 9 specimens without stirrups and under different strength grades(C20,C30,and C40)and 36 specimens under different strength grades(C20,C30,and C40).Moreover,three stirrup levels(rectangular,diamond-shaped compound,and spiral stirrups)and different stirrup spacings(40,50,60,and 70 mm)were used.Subsequently,the stress−strain curves of specimens subjected to axial loading were measured.The effects of the stirrup spacing and stirrup configurations on the stress and strain were investigated,respectively,and the lateral effective stress of the different stirrups was calculated based on the cohesive-elastic ring model and modified elastic beam theory.Moreover,a damageconstitutive model of CAC considering the lateral stress was set up based on damage mechanics theory.The results indicated an increase in the stress and strain with a decrease in the stirrup spacing,and the adopted stirrup ratio had a better strengthening effect than the different concrete grades,and the variation in the deformation was restricted by the performance of coral coarse aggregate(CA).However,an increment in the lateral strain was observed with an increase in the axial strain.The lateral stress model showed a good agreement with the experimental data,and the proposed damageconstitutive model had a good correlation with the measured stress−strain curves.